How can I free a stuck isolator valve in an awkward position? Toilet is leaking.

[Gary111]

Hi, my toilet is dripping from where the 15mm pipe joins to the inlet valve. I’m not sure if the plastic on the inlet selves thread may be cracked?

There’s main stop tap is very tricky to undo once tightened, it’s on lead pipe so ideally don’t want to mess with that.

It’s a boxed in toilet which we have had several problems with.
I found an isolator valve once I chipped off some of the tiles, but it’s not been used for ages and I just can’t shift it.
Any ideas how to get the water off to work on the leaky toilet joint please?

 

[Gary111]

Here are the pics

 

[CountryFan]

Unless you can turn off the boundary (usually in the street/pavement) then turn off main stopcock and renew the isolation valve. Failing that use a pipe freezing kit.